Polyaniline has received increased interest for industrial applications (See, e.g., “Plastics that Conduct Electricity” by R. B. Kaner et al., Scientific American 258, 106 (1988)). Chiral conducting polymers are particularly interesting for industrial applications including, e.g., surface-modified electrodes, chemical separation materials, self assembled monolayers, light emitting devices, light filters (Bragg filters), and liquid crystalline devices. Chiral polyaniline has been previously described. In “Chemical Generation of Optically Active Polyaniline via the Doping of Emeraldine Base with Camphorsulfonic Acid” by Majidi, et al., Polymer 36, 3597 (1995), it was disclosed that optically inactive polyaniline could be converted to optically active polyaniline by dissolving the emeraldine base form of polyaniline (EB) in n-methyl-2-pyrrolidinone and adding either (+)- or (−)-camphorsulfonic acid (CSA). More recently, chiral polyaniline was electrochemically synthesized by polymerizing an aqueous solution of aniline in the presence of either (+)- or (−)-CSA (See, e.g., “Facile Preparation of Optically Active Polyanilines via the In Situ Chemical Oxidative Polymerization of Aniline” by Norris et. al., Synthetic Metals 106, 171 (1999)).
Nanostructured materials have attracted much attention for a variety of potential applications.
Water-soluble, chiral polyaniline nanocomposites have been synthesized by electrochemically polymerizing aniline in the presence of optically pure CSA and a dispersant, either polystyrene sulfonate or colloidal silica (See, e.g., “Electrochemical Formation of Chiral Polyaniline Colloids codoped with (+)- or (−)-10-Camphorsulfonic Acid and Polystyrene Sulfonate” by Barisci et al., Macromolecules, 31, 6521 (1998); “Preparation of Chiral Conducting Polymer Colloids” by Barisci et al., Synthetic Metals, 84, 181 (1997); and “Electrochemical Preparation of Chiral Polyaniline Nanocomposites” by Aboutanos et al., Synthetic Metals, 106, 89 (1999).).
Sun et al. and Liu et al. achieved the template-guided synthesis of water-soluble non-chiral polyaniline complexes by polymerizing an aniline monomer in the presence of a polyelectrolyte (See, e.g., Sun et. al., American Chemical Society Polymer Preprints, 33, 379 (1992), Sun et. al., Materials Research Society, Symposium Proceedings, 328, 209 (1994); Sun et al., Materials Research Society, Symposium Proceedings, 328, 167 (1994); and Cushman et al., Journal of Electroanalytical Chemistry, 291, 335 (1986)). The final product is a double-stranded polymer complex in which the polyaniline and the template (polyelectrolyte) are bound by electrostatic interaction (See, e.g., Sun et al., Synth. Metals 84, 67 (1997) and U.S. Pat. No. 5,489,400 by Liu et al. for “Molecular Complex of Conductive Polymer and Polyelectrolyte; and a Process for Producing Same”). Such polyaniline complexes are water soluble because of the hydrophilic nature of the polyelectrolyte. The above references teach that template-guided syntheses are carried out stepwise. First, the template (a pre-formed polymer) and the monomer of the conducting polymer to be prepared are assembled into an adduct, the acidity of the adduct solution is then adjusted, and the polymerization is initiated.
U.S. Pat. No. 6,090,985, by MacDiarmid et al. for “Chiral Polyanilines and the Synthesis Thereof”, describes the chemical synthesis of chiral polyanilines which includes polymerizing an aniline monomer in the presence of a chiral dopant acid, an oxidizing agent and, optionally, a substrate. While the products of this synthesis were not described as nanostructures, such as nanofibers and the like, close examination of the product from an example in accordance with example 1 of this patent revealed a nanostructured, nanofiber-like product. However, low chirality levels were reported by MacDiarmid et al. for the resultant chiral polyanilines which is consistent with the low chirality levels found by the present applicants in the repeat of example of this patent.
A need remains for a procedure of forming polyaniline materials with relatively higher chirality than presently available. After extensive and careful investigation, applicants have now prepared polyaniline having high levels of chirality and nanostructured polyaniline having high levels of chirality.